Production of lubricating oils by hydrotreating and distillation

ABSTRACT

A NARROW CUT LUBRICATING OIL STOCK, PARTICULARLY A LOW GRADE STOCK, IS HYDROTREATED AND THEN FRACTIONATED TO PRODUCE A LIGHT FRACTION OF MEDIUM VISCOSITY INDEX AND A HEAVY FRACTION OF HIGH VISCOSITY INDEX.

United States Patent US. Cl. 208-264 '8 Claims ABSTRACT OF THE DISCLOSURE A narrow cut lubricating oil stock, particularly a low grade stock, is hydrotreated and then fractionated to produce a light fraction of medium viscosity index and a heavy fraction of high viscosity index.

This application is a continuation-in-part of our copending application, Ser. No. 755,746, filed Aug. 27, 1968, now abandoned.

This invention relates to the production of lubricating oils of improved properties. More particularly, it is concerned with the production of high viscosity index oils from charge stocks of low or medium viscosity index. In its more specific aspects, it is concerned with the simultaneous production of medium and high viscosity lubrieating oils from narrow cut lubricating oil fractions obtained from low quality paraffinic crudes such as South Louisiana Light Regular.

The up-grading of lubricating oil stocks is Well known in petroleum refining. Lubricating oils are conventionally refined by methods including distillation, solvent refining, acid treating, clay contacting and solvent dewaxing. In these processing steps distillation is employed as a means of separating the crude oil into fractions of suitable viscos ity. Solvent refining using for example furfural, sulfur dioxide or phenol is ordinarily used to improve the viscosity index of the treated oil. Acid treating is employed to improve the oils color, stability, and resistance to oxidation. Clay contacting is used to improve the color of the oil and is also used after acid treating to neutralize the oil. Solvent dewaxing is used to lower the pour point of the oil.

Although all of these listed characteristics are important perhaps one of the most important qualities that a lubricating oil should have particularly those oils subjected to wide variations in temperature is a high viscosity index, an indication of the resistance of the oil to change in viscosity with change in temperature. Customarily, the viscosity index of an oil is improved by contacting the lubricating oil charge stock with a solvent for aromatics, separating the aromatic rich extract phase from the railinate phase, separating the solvent from the rafiinate by distillation and recycling the solvent to the extraction zone. The rafiinate may then be further treated to improve its properties such as by solvent dewaxing or any other of the various steps listed above. Although solvent refining is effective in increasing the viscosity index of the treated oil, it ordinarily does not reduce the viscosity of high viscosity oils to as great an extent as is frequently desired.

Another method for upgrading lubricating oil stocks is termed hydrorefining. In this process as conventionally practiced, a wide boiling range lube oil stock is contacted in the presence of hydrogen with a catalyst at elevated temperature and pressure. However, this process gives a wide boiling range product which is unsuitable for many applications.

3,691,067 Patented Sept. 12, 1972 ice It is an object of the present invention to provide a process for up-grading hydrocarbon lube oil stocks. Another object is to reduce the viscosity of highly viscous lube oil fractions. Another object is the simultaneous production of medium and high viscosity index lube oil fractions from low quality paraifinic crudes. Still another object is the production of lubricating oils having high viscosity indices usually only obtainable through the use of additives. These and other objects of the invention will be obvious to those skilled in the art from the following disclosure.

According to the process of our invention a narrow cut lubricating oil fraction is contacted in the presence of hydrogen with a catalyst under controlled conditions of temperature, pressure and space velocity to produce an oil of improved viscosity index and this product oil is then fractionated into a lighter fraction of medium viscosity index and a heavier fraction of high viscosity index. The ratio of fractionation of light to heavy fractions is determined by the desired product viscosities and viscosity indices and by charge stock quality (i.e. viscosity index).

The lubricating oil charge stocks used in the process of our invention are narrow cut lubricating oil fractions having a boiling range not extending over about 250 F. and preferably boiling within a range of about 200 F. Ordinarily it is more practical to charge low quality stocks, for example, those having a viscosity index of 6085 although the process is equally applicable to charges having a higher viscosity index. Suitable charge stocks include those obtained from refined lube oil stocks, low quality paraflin stocks, raw distillates, deresined, decarbonized or deasphalted residual stocks, naphthene base oils and the like.

The temperature in the hydrotreating zone should be maintained between about 600 and 800 F., preferably between 650 and 775 F. Temperatures in excess of 800 F. should be avoided as they cause an undesirably excessive amount of cracking. The partial pressure of the hydrogen should be maintained between 1000 and 3000 p.s.i.g. and preferably between 1300 and 2500 p.s.i.g. The liquid hourly space velocity (volumes of oil per volume of catalyst per hour) may range from 0.1 to 1.5, a preferred space velocity being in the range of 0.25 to 1.0. Space velocities below 0.1 should also be avoided as they result in excessive cracking. Actually the space velocity should be correlated with the temperature so that cracking is minimized. Hydrogen rates of 2000 to 15,000 s.c.f.b. (standard cubic feet per barrel) may be used although hydrogen rates of 5000 to 10,000 s.c.f.b. are preferred. The hydrogen need not necessarily be pure, gases containing 60% or more hydrogen having been found satisfactory.

Catalysts used in the process of our invention may be supported or unsupported. The active component of the catalyst comprises an oxide or sulfide of a metal such as iron, cobalt, nickel, molybdenum, tungsten, vanadium, manganese and the like and mixtures thereof having hydrogenating activity. Specific examples of catalysts are cobalt molybdate, nickel tungsten sulfide, cobalt sulfide, molybdenum oxide, or molybdenum sulfide. The catalyst may be supported on a porous material such as alumina, magnesia, zirconia, silica, spinels and the like. The support is an inert material which results in a catalyst having substantially no cracking activity. The catalyst may be employed as a fixed bed, a fluidized bed, or as a slurry in the oil. However the catalyst should be in such a form that adequate contact between the catalyst and the oil is obtained. Preferably, the catalyst is in the pellet or extrudate shape and is used in the form of a fixed bed. Although the catalyst has essentially no cracking activity,

some cracking will take place due to the elevated temperature of the hydrogenation reaction but it is kept to a minimum by regulating the temperature and space velocity so that a lube oil yield of at least 60 volume percent is obtained.

The following examples are submitted for illustrative purposes only and should not be construed as limiting the invention in any manner.

EXAMPLE I This example shows the eifect on the product of varying the space velocity. The catalyst here is a sulfided nickel tungsten supported on alumina and containing 6% nickel and 19% tungsten by weight. The charge has a boiling range of from 740 F. IBP to 815+ F. 90% Point by Hempel distillation. The characteristlcs of the charge and product and reaction conditions are tabulated below. The product Oil is stripped under vacuum with nitrogen sweep to obtain a product havlng a flash polnt comparable to that of the original charge.

TABLE I Charge:

RI at 70 C 1.4721 Gravity API. 2 Flash COO, 400 Viscosity SUS at 100 F 140 Viscosity index 76 Pour, F +80 Hydrotreating conditions:

Reactor temperature, F 775 775 Reactor pressure, p.s.i.g 1, 500 1, 500 Space velocity, LHSV 0. 50 0.25 Hydrogen rate, s.c.i.b 5,000 5,000 Product oil (stripped):

R1 at 70 C 1. 4587 1. 4538 Gravity, 31. 7 32. 9 Flash, 000, F- 395 405 Viscosity, SUS, 100 03.1 83.8 V 105 113 Pour, F. +80 +80 Lube oil yield, vol. percent 73. 9 62. Fractionated product: 30% overhead:

R1 at 70 0 1. 4017 1. 4530 30.9 31.2 74. 2 68.3 78 105 70% bottoms:

RI at 70 C 1. 4582 1. 4532 Gravity, API 32. 1 34. 3 Viscosity, SUS, 100 IL 105.1 03.0 VI 110 117 EXAMPLE II This example shows that the process of our invention is applicable not only to low quality charge stocks but also to medium quality lubricating oil stocks. The catalyst in the example is the same as in Example I. Boiling range of the charge is 650 F. IBP to 850 F. 90% Point by Hempel distillation. The characteristics of the charge and product and the reaction conditions are tabulated below.

TABLE II Charge:

RI at 70 C Viscosity, SUS at l OO Hydrotreating conditions:

Reactor temperature, F Reactor pressure, p.s.i.g Space velocity, LIISV Hydrogen rate, s.c.f.b 5,000

Product oil (stripped):

RI at 70 C 1.4576 Gravity, API 32. 7 Flash, COO, F... 385 Viscosity, SUS, 100 81.7 \I.. 107 Pour, 1 +85 Waxy lube oil yield, vol. percent 05.0

TABLE IIContinued Fractionated Product R1 at Gravity, Viscosity, Cut Nos 0. AII SUS, 100 F. VI

30% overhead. 70% bottoms EXAMPLE III This example shows that the process of our invention is applicable not only to low quality charge stocks but also to high quality deresined straight run stock from Pennsylvania Crude. The catalyst in this example is the same as in Examples I and II. The characteristics of the charge and product and the reaction conditions are given in Tables III and IV. The amount of product taken overhead from stripped oil depends on the desired product viscosity since the stripped oil itself is satisfactory as a refined oil needing only a finishing process to be satisfactory as a finished base oil.

TABLE III Charge:

RI at 70 C 1. 4789 Gravity, API 2. 68 Flash, COC, F 525 Viscosity, SUS/100 FJ- 2,155, 2, 109 Viscosity, SUS/210 F 143.0,142. 9 Viscosity, index 100, 99 Pou F Carbon residue, perccn 1. 33

Hempcl fractionation Vis- Viscosity, cosity, Vis- Gravity, SUS/ SUS/ cosity, API I. 210 F. index 1 Extrapolated by H values. 2 Corrected, top tower temp. at end of cut.

TABLE IV Hydrotreating conditions:

Reactor temperature, F 800 Reactor pressure, p.s.i.g 1,400 LH V 0. 5 S.c.f. Hilbarrel 5, 200

Waxy Dewaxed Stripped oil tests:

Gravity 29. 3 29. 0 Flash, 420 415 Viscosity, SUS/100 FA. 290 337, 338 Viscosity, SUS/210 F 55. 2 56. 9, 57 2 Viscosity index..." 126 114,115 Pour F +105 10, 10 Yield, vol. percent 64. 6

Hempel fractionation of stripped 011 product (waxy) Vis- Vis- Gravcosity, cosity, Visity, SUS SUS/ cosity, Pour, AP 100 F. 210 F. index F.

1 Extrapoiated by H values. 2 Corrected.

EXAMPLE IV In this example the charge stock is a heavy raw wax distillate having a boiling range of 880 F. (10% overhead) to approximately 975 F. (90% overhead) by Hempel distillation. The characteristics of the total charge and cuts from Hempel distillation of the total charge are given in Table V below.

The charge is contacted with the same catalyst as in Examples 1 and III. The product is then stripped to a satisfactory flash point and solvent dewaxed to 10 F. pour point. Test results of the waxy and dewaxed oils are given in Table VI. The hydrotreated solvent dewaxed oil is fractionated into approximately 10 volume percent cuts. The viscosity index distribution shows this oil readily adaptable to be fractionated into a light and heavy fraction with the heavy fraction having a desirable VI level while the light fraction is acceptable as a light lube having a low or medium VI.

v01 Gravity, percent AP l Extrapolated by H values. Top tower temperature (corrected) at end of cut. 3 Estimated.

TABLE VI Hydrotreating conditions:

Reactor ternpzztture, F 775 Reactor pressure, p.s.i.g 1, 500 LHSV 0.24 S e v Hz/bbL- 5, 00

Waxy Dewaxed Stripped oil tests:

Gravity, API 28. 5 27. 5 Flash, COO, F 400 Viscosity, BUS/100 F 148.6 163.4 Viscosity, SUB/210 F 43. 8 43. 8 Viscosity index 113 93 Pour, F 110 Yield, vol. percent 78. 5

Hempel fractionation of stripped oil product (dewaxed) Vis- Vis- Cum. Gravcosity, cosity, Visvol. ity, S/ SUS/ cosity, Pour, percen API 100 F. 0 F. index Hempel iractionations of stripped oil product (waxy) X Corrected.

The solvent refining of the same charge stock and the subsequent Hempel distillation of the product yields fractions having the following characteristics.

A comparison of the data in Tables V and VH with the data in Table VI shows that the solvent refined product has substantially uniform viscosity index distribution throughout the product as does the charge whereas the product obtained by hydrotreating has an unexpected increase in the viscosity index of the heavier fractions. It will also be noticed that the heavier hydrorefined product has a much lower viscosity than the heavier portion of the solyent refined product.

The terms low, medium and high when used in connection with viscosity index are to be construed in a relative sense and are not to be considered as having definite numerical values. For example a low viscosity index charge is treated to produce a fraction of medium viscosity index, i.e. higher than the charge but lower than the product fraction of high viscosity index. It is thus possible that the viscosity index of a particular charge stock can be higher than that of the medium viscosity index product fraction of a different charge stock.

Obviously, various modifications of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for the simultaneous production of a medium viscosity index lubricating oil and a high viscosity index lubricating oil which comprises contacting a narrow cut lubricating oil charge stock having a boiling range extending over not more than about 250 F. with hydrogen in the presence of a hydrogenating catalyst having essentially no cracking activity comprising a hydrogenating component supported on an inert material at a pressure between about 1000 and 3000 p.s.i.g. a temperature between 650 and 775 F., a space velocity between 0.1 and 1.5 and a hydrogen rate between 2000 and 15,000 s.c.f.b., said temperature and space velocity being correlated to produce substantially no cracking, recovering a lubricating oil from the hydrogenation zone effluent and separating the recovered lubricating oil into a light fraction having a viscosity index higher than said narrow cut lubricating oil charge stock and a heavy fraction having a viscosity index higher than said light fraction.

2'. The process of claim 1 in which the narrow cut lubricating oil charge stock comprises a solvent refined neutral oil.

3. The process of claim 1 in which the narrow cut lubricating oil charge stock has a viscosity index between 60 and 105.

4. The process of claim 1 in which the narrow cut lubricating oil charge stock comprises a paraflinic distillate.

5. The process of claim 1 in which the catalyst comprises sulfided nickel and tungsten.

6. The process of claim 1 in which the charge stock comprises a solvent refined neutral oil and the heavy frac- 7 8 tion of the product has a viscosity index of not less than 3,308,055 3/1967 Koziowski 20818 120. 3,481,863 12/1969 Donaldson et a1 20818 7. The process of claim 1 in which the charge stock 3,50 555 4 1970 w i et 208 18 comprises a aphthene base oil. 3,520,796 7/ 1970 Murphy et a1. 20818 8. The process of claim 1 in which the charge stock 5 is selected from the group consisting of deasphalted, decarbonized, and deresined residue, HERBERT LEVINE References Cited CL UNITED STATES PATENTS 10 208143, 18

2,960,458 11/1960 Beuther et a1. 20819 3,242,068 3/1966 Paterson 20818 Primary Examiner 

